A typical fork or steerer assembly generally includes a fork crown that cooperates with a pair of downward extending legs. A steerer tube extends in an upward direction from the fork crown and cooperates with a head tube of a bicycle frame. The steerer tube can be integrally formed with one or more of the fork crown and forks or the steerer tube and fork crown can be constructed with mating securing structures, such as geometric, threaded, and/or bonded connections. Regardless of the specific construction, the steerer tube is commonly centrally positioned relative to the fork crown and is secured to the fork crown so as to extend in a direction generally opposite the pair of fork legs.
The steerer tube, fork crown, and fork legs can be constructed of any of aluminum or metal-type materials, composite materials, and/or carbon based materials such as carbon fiber material and/or a glass fiber material. A stem and handlebar are commonly engaged with the steerer tube such that the head tube of the bicycle frame is captured between the stem/handlebar and the fork crown. A number of rolling support elements, such as bearings, are commonly disposed between the head tube and the steerer tube and facilitate generally smooth rotational movement of the steerer assembly relative to the bicycle frame.
A front wheel is commonly disposed between the fork legs and supports the forward portion of the bicycle. Although a portion of the loading imparted to the front wheel during use of the bicycle is absorbed by flexure of the respective portions of the steerer assembly, a majority of the front wheel load is communicated to the bicycle frame through the interaction of the steerer tube and the head tube. A portion of this loading is communicated to the rider through their interaction with the handlebars. Rider steering inputs are communicated in a generally reverse direction from the handlebars and through the steerer assembly to effectuate a desired turning operation. The communication of the impact and steering forces through the steerer assembly directly affects ride experience.
During riding, although the front wheel can be subjected to loading in a variety of radial directions, these loading are commonly directed in a longitudinal and a lateral direction. As used herein, the longitudinal direction generally refers to directions aligned with a longitudinal axis or a direction of travel of the bicycle. Understandably, the longitudinal direction includes both generally forward and generally rearward directions, or the fore and aft directions, relative to the longitudinal axis of the bicycle. The lateral directions refer to the generally right and generally left directions relative to the longitudinal axis of the bicycle. That is, the generally opposite left and right sides of the bicycle as compared to the forward and rearward portions of the bicycle.
Many riders' associate bicycle handling performance with the responsiveness of the front wheel assembly to steering inputs. The laterally oriented interaction between the steerer tube and the head tube is largely associated with the rider's perception of handling performance. Improved handling performance can be attained with increased lateral stiffness of the steering assembly. Said in another way, increasing the lateral stiffness of the steerer assembly provides a steering system that is more responsive to steering inputs.
Others have provided bicycles with a desired degree of steering responsiveness. Such systems include a larger diameter bearing support between the steerer tube and the head tube. Such a configuration offsets the lateral support in a direction laterally outboard of the longitudinal axis of the steering assembly. Unfortunately, such an approach has several detrimental effects on the overall construction of the bicycle and steerer assembly.
Such assemblies increase the size and mass of the respective components of the steering assembly thereby undesirably increasing the weight of the bicycle. Furthermore, such a configuration increases the rigidity of the steerer assembly in a generally radially uniform manner. That is, in addition to increasing the rigidity of the steerer assembly in the opposite lateral directions, such an approach also undesirably increase the rigidity in the generally opposite fore and aft directions. The increase in the fore and aft rigidity of the steerer assembly detrimentally affects the fore and aft stiffness performance of the steering assembly by communicating greater amounts of the fore and aft directed loading of the front wheel to the rider. As such, such systems adversely affect rider comfort by communicating a greater amount of road bumps and/or impacts to the hands of the rider.
Therefore, it would be desirable to have a steerer assembly with improved lateral and fore and aft stiffness performance. It is further desired to provide steerer assembly that can be efficiently and repeatably produced and is robust and lightweight.